1. Field of the Invention
The present invention relates generally to factory systems and, more particularly, to a closed loop demand fulfillment system for mass-producing build-to-customer-order items.
2. Description of the Related Art
Scheduling work in a manufacturing environment is a complex process. Most factories use an automated planning and scheduling system to ensure that customer demand is satisfied in a timely manner with minimum inventory. To achieve this goal, such planning requires that work for each manufacturing line is efficiently scheduled, that the appropriate materials needed to complete each task performed are available when needed on the manufacturing line, and that products are manufactured in the order that the products are needed. To produce a manufacturing schedule, customer orders must be received and analyzed, priorities must be assigned to items to be manufactured, manufacturing resources must be allocated, work must be scheduled, raw materials and/or parts must be obtained and delivered to the manufacturing line, work in progress must be tracked, and variability in availability of raw materials and/or parts must be handled. Many manufacturing facilities plan and manage these many tasks by combining multiple computerized planning and scheduling systems with paper-based management systems.
An example of a widely-used commercially available automated planning and scheduling system is i2 Technologies, Inc.'s Factory Planner and Rhythm Collaboration Planner. The i2 Factory Planner generates work schedules and material requirements schedules using customer-provided inputs of demand and inventory. The i2 Rhythm Collaboration Planner helps organizations to quote and promise order delivery to customers in real-time while obeying customer constraints on lot sizes, number of shipments, and time between shipments. The i2 Rhythm Collaboration Planner helps provide a global view of the entire supply chain from sourcing to delivery. These products handle the complicated scheduling for large, distributed, complex manufacturing environments. However, any automated planning and scheduling system can only produce accurate results if inputs to the system are accurate.
Most businesses schedule manufacturing activities based upon forecasts of demand for products. Work is typically scheduled on a daily or weekly basis to meet demand predicted based on past sales. Inputs to the automated planning and scheduling system are demand forecasts.
To ensure that demand is satisfied, most factories maintain inventories of both parts and/or raw materials. Each type of inventory typically includes stock to accommodate the average usage rate and stock to meet variations in demand. However, maintaining high inventory levels does not necessarily guarantee that the right inventory is available when and where it is needed. A material delivery schedule is needed that delivers material to the manufacturing line prior to the time the material is needed during manufacturing.
Furthermore, due to limited space in most factories and the expense of maintaining warehouses of inventory, it is desirable to maintain only the minimum inventory necessary to meet demand. Some factories operate on a build-to-customer-order model where no product is manufactured unless it has been ordered by a customer. This model enables the factory to operate with minimal inventory of finished products, but does not address the inventories of materials.
In addition to minimizing material inventory, it is also desirable to minimize material handling to ensure that materials are delivered to the right location at the right time.
Problems with scheduling manufacturing activities are exacerbated in a mass production manufacturing environment for commodities that are built to customer orders. The term commodity is used herein to describe a mass-produced unspecialized product. In such an environment, the timeframes for manufacturing and delivery activities may be sub-hourly. Demand forecasts do not reliably predict material needs at this level, and schedules based upon demand forecasts become less and less accurate as time elapses between the time the work is scheduled and the time the work is initiated on the manufacturing line. Nor do demand forecasts respond to variations in material needs resulting from atypical customer orders. Scheduling based upon demand forecasts does not provide the responsiveness to changes in inventory and work schedules needed to ensure that materials are delivered to the right place at the right time.
A further problem in scheduling work and material deliveries for performing the work is that a current state of the available inventory, updated sufficiently often to keep up with consumption of material, is very difficult to obtain. Materials can reside in many locations, or material sources, within the factory. For example, the material may reside as part of work in progress at an operation on a manufacturing line, the material may reside in a stockroom, or the material may be in transit from one material source to another. The material may also be available from a supplier that is close enough so that the material could be used on the manufacturing line a few hours later.
Typically no automated system keeps track of the quantities of material available at all of these different locations. For example, an in-house inventory is typically tracked using an in-house inventory management system, whereas supplier inventory is tracked in the supplier's own inventory management system. Furthermore, materials residing in the factory but on a manufacturing line as part of work-in-progress are usually not considered to be sources of supply of materials for scheduling work and material deliveries. These work-in-progress materials are typically considered to be unavailable until they can be counted during a time period when manufacturing is halted, such as in an overnight batch process. Material in-transit from one material source to another is also typically excluded from a calculation of available supply of materials because it is difficult to determine the quantity of the material as they are moved in the time periods necessary for mass-producing items.
Even if each of the systems including all available inventory for all materials is maintained in real time, additional processing time is necessary to obtain the available inventory of all materials at all material sources and combine them to provide a current state of the available inventory of materials. As the work schedule and the material delivery schedule are being generated, material is being consumed and customer orders are being fulfilled. This additional processing time should be minimized to ensure that outstanding customer orders and the current state of the available inventory are as accurate as possible for generating the schedules when they are needed.
What is needed is a demand fulfillment system and method for scheduling work and delivery of material for mass producing items in a factory based upon current supply and demand. For example, outstanding customer orders for items are an accurate measure of current demand, and a current state of an available inventory of material for producing the items is an accurate measure of current supply. All customer orders should be considered a source of demand from the time the customer order is received until the customer order is fulfilled. Similarly, all material available to the factory, regardless of its location, should be considered when producing a work schedule and a material delivery schedule. It should be possible to determine current supply and demand while manufacturing is occurring in the factory, without the need to delay manufacturing or to wait until a lull when the customer orders and the available inventory are static. It should be possible to generate a work schedule and a material delivery schedule as often as is necessary to keep up with consumption of materials and fulfillment of customer orders.